The present invention relates generally to bovine mastitis infections caused by Staphylococcus aureus and, more particularly, to vaccines derived from selected strains of Staphylococcus aureus. 
Bovine mastitis is the most important infectious disease affecting both the quality and quantity of milk production. Staphylococcus aureus (i.e., xe2x80x9cS. aureusxe2x80x9d) is the prime agent causing bovine mastitis, and it is difficult to eliminate. In different countries, the prevalence of S. aureus mastitis ranges from 10% to 40% of all cows. The infected animals may serve as reservoirs of infection endangering other dairy cattle in the herd (Fox, L. K. and Hancock, D. 1989, xe2x80x9cEffects of segregation on prevention of intramammary infection by Staphylococcus aureusxe2x80x9d, J. Dairy Sci. 72:540-544).
Recent estimates suggest that the annual production losses due to S. aureus are over 15 million dollars in Israel and over 2 billion dollars in the USA. The prevalence of S. aureus mastitis in dairy cattle raises several concerns. This bacterium can cause severe damage to milk-synthesizing tissues, drastically reducing milk production and altering milk composition. For more information on bovine mastitis and its effects, see, for example: (1) Oliver, S. P., Sordillo, L. M, 1988, xe2x80x9cUdder health in the periparturient periodxe2x80x9d, J Dairy Sd. 71:2584-2606; (2) Postle, D. S., Roguinsky, M., Poutrel, B., 1978, xe2x80x9cInduced Staphylococcal infections in the bovine mammary glandxe2x80x9d, Am J Vet Res. 39:29-35; (3) Sordillo, L. M., Nickerson, S. C and Akers, R. M., 1989, xe2x80x9cPathology of mastitis during lactogenesis: Relationships with bovine mammary structure and functionxe2x80x9d, J. Dairy Sci. 72: 228-240; (4) Watson, D. L., McColl, M. L., Davies, H. I., 1996, xe2x80x9cField trial of a Staphylococcal mastitis vaccine in dairy herds: clinical, subclinical and microbiological assessmentsxe2x80x9d, Aust. Vet. J. 74:447-450.
Depending on the duration and the severity of the infection, the productive performance of dairy cattle may be diminished permanently. Therefore, the development of effective methods of controlling S. aureus mastitis will increase profitability to dairy producers by reducing costs. So far, post-milking teat disinfection and antibiotic therapy are the only widely accepted methods of mastitis control (National Mastitis Council, 1987, xe2x80x9cCurrent concepts of bovine mastitisxe2x80x9d, Arlington, Va.).
These methods are not cost-effective due to milk loss during and after antibiotic therapy. Moreover, antibiotic therapies formulated for intramammary use are generally unsuccessful in eliminating existing S. aureus infections or preventing the establishment of chronic diseases (Ziv, G., 1995, xe2x80x9cTreatment of Mastitis: An overview of progress during the last ten yearsxe2x80x9d, Proc. The 3rd Internal Mastitis Seminar, Tel Aviv, Israel 2-12).
There is also a growing concern over the presence of drug residues in the food supply as a consequence of these procedures. To date, culling chronically infected cows is often the only practical means of eliminating S. aureus from a herd.
Vaccination is a logical approach for controlling infectious diseases in food producing animals. However, the paucity of information regarding relevant antigens remains a major deterrent to successful immunization against S. aureus mastitis. To our knowledge, the known, commercially available S. aureus vaccines have shown limited efficacy under field conditions. See, for example:
In the USA:
1) Nickerson, S. C., Owens, W. E., Bodie, R. L, 1993, xe2x80x9cEffect of a Staphylococcus aureus bacterin on serum antibody, new infection, and mammary histology in non lactating dairy cowsxe2x80x9d, J. Dairy Sci., 76:1290-1297;
2) Sears, P. M., Norcross. N. L., Kenny, K., Smith, B., Gonzalez, R. N., Romano, M. N., 1990, xe2x80x9cResistance to Staphylococcus aureus infections in staphylococcal vaccinated heifersxe2x80x9d, Proc. Internatl. Symp. Bovine Mastitis, Indianapolis, Ind., p. 69.
3) Sordillo, L. M., Nickerson, S. C and Akers, R. M., 1989, xe2x80x9cPathology of mastitis during lactogenesis: Relationships with bovine mammary structure and functionxe2x80x9d, J. Dairy Sci., 72: 228-240; and
4) Yoshida K., Ichiman, Y., Narikawa, S., Evans, G. B., 1984, xe2x80x9cStaphylococcal capsular for preventing mastitis in two herds in Georgiaxe2x80x9d, J. Dairy Sci., 67:620-627.
In Australia:
1) Watson, D. L., 1984, xe2x80x9cEvaluation of attenuated, live staphylococcal mastitis vaccine in lactating heifersxe2x80x9d, J. Dairy Sci., 67:2608-2613;
2) Watson, D. L., Schwartzkoff, C. L., 1990, xe2x80x9cA field trial to test the efficacy of a staphylococcal mastitis vaccine in commercial dairies in Australiaxe2x80x9d, International Symposium on Bovine Mastitis, National Mastitis Council, Arlington, 73-76;
3) Watson, D. L., 1992, xe2x80x9cVaccination against experimental staphylococcal mastitis in dairy heifersxe2x80x9d, Res. Vet. Sci., 53:346-353; and
4) Watson, D. L., McColl, M. L., Davies, H. I., 1996, xe2x80x9cField trial of a Staphylococcal mastitis vaccine in dairy herds: clinical, subclinical and microbiological assessmentsxe2x80x9d, Aust. Vet. J., 74:447-450.
In Norway:
1) Nordhaug, M. L., Nesse, L. L., Norcross, N. L., Gudding, R., 1994, xe2x80x9cA field trial with an experimental vaccine against Staphylococcus aureus mastitis in cattle. I. Clinical parametersxe2x80x9d, J Dairy Sci., 77:1267-1275;
2) Pankey, J. W., et al., 1985, xe2x80x9cEvaluation of protein A and a commercial bacterin as vaccines against Staphylococcus aureus mastitis by experimental challengexe2x80x9d, J. Dairy Sci., 68:726-731; and
3) Yoshida K., Ichiman, Y., Narikawa, S., Evans, G. B., 1984, xe2x80x9cStaphylococcal capsular for preventing mastitis in two herds in Georgiaxe2x80x9d, J. Dairy Sci., 67:620-627.
For the most part, these conventional vaccines have not prevented the disease and show only a marginal benefit in ameliorating the severity and duration of clinical symptoms of S. aureus mastitis. Traditional S. aureus mastitis vaccines have included killed or attenuated bacteria, toxoids, and cell wall extracts from selected laboratory or field strains. See: (1) Nickerson, S. C.; (2) Sears, P. M.; (3) Watson, D. L. 1984; and (4) Watson, D. L., 1992; as cited above.
These previous attempts have not considered the significant variation among the different strains of S. aureus which cause mastitis.
Attempts to solve this problem are described in U.S. Pat. No. 4,840,794. However this solution has not been satisfactory.
It is, therefore, desirable to develop a vaccine which would overcome the above disadvantages and would prevent the occurrence of bovine mastitis infection or at least control such infections to a large extent.